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Re: [PATCH -mm] kprobes: kprobe-booster for ia64
- From: Masami Hiramatsu <mhiramat at redhat dot com>
- To: Shaohua Li <shaohua dot li at intel dot com>
- Cc: Andrew Morton <akpm at linux-foundation dot org>, LKML <linux-kernel at vger dot kernel dot org>, ia64 <linux-ia64 at vger dot kernel dot org>, "Luck, Tony" <tony dot luck at intel dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Jim Keniston <jkenisto at us dot ibm dot com>, systemtap-ml <systemtap at sources dot redhat dot com>
- Date: Mon, 10 Mar 2008 14:25:44 -0400
- Subject: Re: [PATCH -mm] kprobes: kprobe-booster for ia64
- References: <47D166E7.2050803@redhat.com> <1205120600.20271.3.camel@sli10-desk.sh.intel.com>
Hello Shaohua,
Thank you for reviewing!
Shaohua Li wrote:
> On Sat, 2008-03-08 at 00:01 +0800, Masami Hiramatsu wrote:
>> From: Masami Hiramatsu <mhiramat@redhat.com>
>> +
>> +/* Prepare long jump bundle and disables other boosters if need */
>> +static void __kprobes prepare_booster(struct kprobe *p)
>> +{
>> + unsigned long addr = (unsigned long)p->addr & ~0xFULL;
>> + unsigned int slot = addr & 0xf;
> slot = (unsigned long)p->addr & 0xf ?
You are correct. I'll fix that.
>
>> + struct kprobe *other_kp;
>> +
>> + if (can_boost(&p->ainsn.insn[0].bundle, slot, addr)) {
>> + set_brl_inst(&p->ainsn.insn[1].bundle, (bundle_t
>> *)addr + 1);
>> + p->ainsn.inst_flag |= INST_FLAG_BOOSTABLE;
>> + }
>> +
>> + /* disables boosters in previous slots */
>> + for (; addr < (unsigned long)p->addr; addr++) {
>> + other_kp = get_kprobe((void *)addr);
>> + if (other_kp)
>> + other_kp->ainsn.inst_flag &=
>> ~INST_FLAG_BOOSTABLE;
>> + }
>> +}
>> +
> There is no lock to protect the flag. If one cpu invokes other_kp and
> the other cpu is changing the flag, what's the result?
I think that other cpu never change the flag, because the caller of this
function(__register_kprobe) locks kprobe_mutex in kernel/kprobes.c.
> Thanks,
> Shaohua
Thanks,
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com